JP5943080B2 - Method for deriving equivalent circuit model of power supply smoothing LC filter - Google Patents

Description

  The present invention relates to a derivation method for deriving an equivalent circuit model of a power source smoothing LC filter composed of a choke coil and a smoothing capacitor for stabilizing the output voltage of a direct current stabilized power circuit.

Conventionally, as a method for deriving an equivalent circuit model of this type of power supply smoothing LC filter, for example, there is a method in a switching regulator disclosed in Non-Patent Document 1. In this document, the buck converter PWM (Pulse Width Modulation) switch blocks, divided into LC filter block and the constant voltage control unit blocks, seeking a transfer function X _LC of divided LC filter block. An input / output characteristic of the power supply smoothing LC filter is simulated by the obtained transfer function _XLC to derive an equivalent circuit model of the power supply smoothing LC filter.

  Further, the equivalent circuit model of the power supply smoothing LC filter can be derived from the equivalent circuit models of the inductor and the capacitor constituting the LC filter.

  In Patent Document 1, an RC circuit shown in FIG. 1A and a circuit that can be simulated in the time domain using a frequency-independent resistor (R), capacitance (C), and inductance (L) are shown. One of the RL circuit shown in FIG. 2B and the RCL circuit shown in FIG. 2C is formed as an equivalent circuit model of MLCC (Multi-Layer Ceramic Capacitor). Then, an evaluation function for determining the accuracy of the formed equivalent circuit model is synthesized, and a circuit constant is determined by minimizing the synthesized evaluation function.

  Non-Patent Document 2 discloses a model in which a copper loss resistance DCR is connected in series to a parallel circuit of an inductance L and a core loss resistance ACR shown in FIG. 2 as an equivalent circuit model of an inductor. The same document describes which factor of the inductor represented by the equivalent circuit model affects the voltage conversion efficiency.

Baba Seitaro "The Key to Success in Power Supply Circuit Design", CQ Publishing, August 1, 2009, 2nd Edition, p253-p256 “1. Investigation of inductor factors affecting power conversion efficiency (step-down)”, Technical Information / Technical Guide / Murata Manufacturing, [online], [Search June 12, 2012], Internet <URL: http: //www.murata.co.jp/products/power_inductor/tech_guide/tech_info.html>

JP 2002-259482 A

  In recent years, for the purpose of cost reduction, the number of trial productions in product development has been reduced and the trial production period has been shortened. For this reason, the importance of simulating the characteristics of prototypes in advance has increased more than before, and in order to reduce the number of prototypes and shorten the trial period, it is indispensable to perform accurate simulations. In the simulation in the DC stabilized power supply circuit design, it is required to accurately derive an equivalent circuit model of the power supply smoothing LC filter.

  However, since the characteristics of the choke coil constituting the DC stabilized power supply circuit depend on the output current of the power supply circuit and the smoothing capacitor depends on the output voltage of the power supply circuit, the power supply disclosed in the conventional non-patent document 1 described above. In the method of deriving the equivalent circuit model of the smoothing LC filter, it is difficult to accurately represent the characteristics of the power smoothing LC filter during operation of the power supply circuit.

  In addition, in the method for deriving an equivalent circuit model of a capacitor disclosed in Patent Document 1, it is necessary to derive an equivalent circuit model for each value of the DC bias voltage superimposed and applied to the capacitor. When applied to an equivalent circuit model, an equivalent circuit model cannot be derived for an arbitrary output voltage of the power supply circuit.

  Also, the equivalent circuit model of the inductor disclosed in Non-Patent Document 2 does not take into account the superposition characteristics due to the output current, and when applied to the equivalent circuit model of the power supply smoothing LC filter, any output current of the power supply circuit can be obtained. An equivalent circuit model cannot be derived for.

The present invention has been made to solve such problems,
Power source smoothing LC filter for deriving an equivalent circuit model of a power source smoothing LC filter composed of a choke coil and a smoothing capacitor for stabilizing the output voltage of the DC stabilized power circuit from each equivalent circuit model of the choke coil and the smoothing capacitor In the derivation method of the equivalent circuit model of
An equivalent circuit model of a smoothing capacitor is a capacitive circuit formed by connecting a capacitive element and a resistive element in parallel, an inductive circuit formed by connecting an inductive element and a resistive element in parallel, and a capacitive element, an inductive element and a resistor. At least one of the sub-resonant circuits formed by connecting the elements in parallel is configured to be connected in series to the main resonant circuit formed by connecting the main capacitive element, the inductive element, and the resistive element in series,
Measures the capacitance change rate of the smoothing capacitor according to the applied DC voltage to the smoothing capacitor and expresses it as a function with the applied DC voltage as a variable, and stabilizes the DC to the capacitance of the main capacitive element that constitutes the main resonance circuit By multiplying the capacitance change rate according to the DC output voltage of the power supply circuit and correcting the capacitance of the main capacitive element , the equivalent circuit model of the smoothing capacitor is adjusted according to the DC output voltage of the DC stabilized power supply circuit. As a model,
The value of each element constituting the equivalent circuit model of the choke coil is measured for a plurality of levels of DC current flowing through the choke coil, and the impedance of the choke coil is obtained for the plurality of levels. The impedance of the choke coil is obtained by interpolating from the impedance of the choke coil for the obtained multiple levels, so that the equivalent circuit model of the choke coil corresponds to the level of the DC output current of the DC stabilized power supply circuit. It is a model.

According to this configuration, the equivalent circuit model of the smoothing capacitor is obtained by multiplying the capacitance of the main capacitive element constituting the main resonant circuit of the model by the capacitance change rate corresponding to the DC output voltage of the DC stabilized power supply circuit. Then, by correcting the capacitance of the main capacitive element , a model corresponding to the DC output voltage of the DC stabilized power supply circuit is obtained. In the equivalent circuit model of the choke coil, the impedance of the choke coil is obtained for a plurality of levels of DC current flowing through the choke coil, and the impedance of the choke coil for a level between the plurality of levels is obtained by calculating the plurality of levels. Is obtained by interpolating from the impedance of the choke coil, and a model corresponding to the level of the DC output current of the DC stabilized power supply circuit is obtained. Therefore, the equivalent circuit model of the power supply smoothing LC filter derived from the equivalent circuit models of the choke coil and the smoothing capacitor is accurately derived in accordance with the DC output voltage and DC output current of the DC stabilized power supply circuit. The characteristics of the power supply smoothing LC filter during the operation of the power supply circuit are accurately expressed. For this reason, the simulation in the DC stabilized power circuit design is performed with high accuracy, and it is possible to contribute to the reduction in the number of trials and the shortening of the trial period in the DC stabilized power circuit design.
According to the present configuration, the equivalent circuit model of the smoothing capacitor is configured by connecting at least one of a capacitive circuit, an inductive circuit, and a sub-resonant circuit in series to the main resonant circuit, The capacitance change rate corresponding to the DC output voltage of the circuit is multiplied by the main capacitance element constituting the main resonance circuit, and the capacitance of the main capacitance element constituting the main resonance circuit is corrected. For this reason, the characteristic of the main resonance circuit that most significantly represents the characteristic of the smoothing capacitor is corrected, and the capacitance of the smoothing capacitor is corrected most effectively according to the DC output voltage of the DC stabilized power supply circuit.

The present invention also provides:
Using the equivalent circuit model of the smoothing capacitor that has been converted into table data when the equivalent circuit model of the smoothing capacitor is converted into table data and the equivalent circuit model of the power supply smoothing LC filter is derived. The equivalent circuit model of the smoothing capacitor is a model corresponding to the DC output voltage of the DC stabilized power supply circuit,
The measured values of each element constituting the equivalent circuit model of the choke coil are converted into table data for a plurality of levels, and each equivalent of the choke coil converted into table data when the equivalent circuit model of the power source smoothing LC filter is derived. Using the circuit model, the equivalent circuit model of the choke coil is a model corresponding to the DC output current of the DC stabilized power supply circuit.

  According to this configuration, by measuring the measured values of each element constituting the equivalent circuit model of the smoothing capacitor and the measured values of each element for a plurality of levels constituting the equivalent circuit model of the choke coil into table data, When deriving the equivalent circuit model of the power smoothing LC filter, it is easy to select the smoothing capacitor equivalent circuit model according to the DC output voltage of the DC stabilized power circuit and the choke according to the DC output current of the DC stabilized power circuit. An equivalent circuit model of the coil can be derived. For this reason, each equivalent circuit model of the choke coil and the smoothing capacitor at the time of operation of the DC stabilized power supply circuit can be easily reproduced and used.

  Further, the present invention is characterized in that an equivalent circuit model of a smoothing capacitor and an equivalent circuit model of a choke coil for a plurality of levels are converted into table data according to each type of the smoothing capacitor and the choke coil, and are made into a library. .

  According to this configuration, the table data about the measured value of each element constituting the equivalent circuit model of the smoothing capacitor, and the table data about the measured value of each element constituting the equivalent circuit model of the choke coil are the direct current to be simulated. Depending on the type of smoothing capacitor and choke coil used in the stabilized power supply circuit, it can be immediately extracted from the library. For this reason, the equivalent circuit model of the choke coil and smoothing capacitor during operation of the DC stabilized power supply circuit is easily and immediately derived according to the type of smoothing capacitor and choke coil used in the DC stabilized power supply circuit to be simulated. Is done.

  The present invention is characterized in that the equivalent circuit model of the choke coil is configured with a circuit formed by connecting a resistive element in series to a parallel circuit of an inductive element and a resistive element as a minimum unit.

  According to this configuration, the equivalent circuit model of the choke coil is based on the accuracy and purpose of the simulation of the DC stabilized power supply circuit with the minimum unit of the circuit formed by connecting the resistive element in series to the parallel circuit of the inductive element and the resistive element. Depending on the configuration.

The present invention also provides:
A first step for inputting the type of the smoothing capacitor and the choke coil, a second step for inputting each value of the DC output voltage and DC output current of the DC stabilized power supply circuit, and the type input in the first step. The equivalent circuit model of table data prepared in advance for the smoothing capacitor is selected from the library, and the equivalent circuit model of the smoothing capacitor is input in the second step using the equivalent circuit model of the selected smoothing capacitor. The third step of making a model according to the output voltage and the equivalent circuit model of the table data prepared in advance for the type of choke coil input in the first step are selected from the library, and the selected choke coil The equivalent circuit model of the choke coil was input in the second step using the equivalent circuit model of In the second step, using the fourth step as a model corresponding to the current output current, the equivalent circuit model of the smoothing capacitor derived in the third step, and the equivalent circuit model of the choke coil derived in the fourth step A fifth step of deriving an equivalent circuit model of the power smoothing LC filter according to the input DC output voltage and DC output current is executed by a computer, and an equivalent circuit model deriving method of the power smoothing LC filter is executed. A computer program to be configured was configured.

  According to this configuration, the types of the smoothing capacitor and choke coil constituting the DC stabilized power supply circuit to be simulated, and the DC output voltage and DC output current values of the DC stabilized power supply circuit are input to the computer program. Thus, the above-described method for deriving the equivalent circuit model of the power supply smoothing LC filter is caused to function by a computer program. That is, the computer program automatically sets the equivalent circuit model of the smoothing capacitor to a model according to the input type of smoothing capacitor and the DC output voltage of the input value, and the equivalent circuit model of the choke coil is input. The model is determined according to the type of choke coil and the DC output current of the input value. For this reason, the user of this derivation method can specify the types of smoothing capacitors and choke coils constituting the DC stabilized power circuit to be simulated, and the DC output voltage and DC output current values of the DC stabilized power circuit. Just input into the input, and accurate simulation of the DC stabilized power supply circuit can be performed with high accuracy and ease. As a result, even a general user who does not have specialized knowledge about circuit simulation can accurately and easily perform accurate circuit simulation of the stabilized DC power supply circuit.

The present invention also provides a power source smoothing LC filter by accessing a server including the computer program via an Internet network, causing the terminal to execute each step using the computer program from a terminal connected to the Internet network. A method of using a computer program that implements a method for deriving an equivalent circuit model is constructed.

  According to this configuration, the user can easily use the computer program by accessing a server including the computer program from a terminal connected to the Internet network. Therefore, it is possible to provide a large number of users with the method for deriving the equivalent circuit model of the power supply smoothing LC filter according to the present invention.

  According to the present invention, as described above, the characteristics of the power supply smoothing LC filter during the operation of the DC stabilized power supply circuit are accurately expressed. For this reason, the simulation in the DC stabilized power circuit design is performed with high accuracy, and it is possible to contribute to the reduction in the number of trials and the shortening of the trial period in the DC stabilized power circuit design.

It is a circuit diagram which shows the equivalent circuit model of the conventional capacitor | condenser. It is a circuit diagram which shows the equivalent circuit model of the conventional inductor. 1 is a circuit diagram of a step-down DC-DC converter to which a method for deriving an equivalent circuit model of a power supply smoothing LC filter according to an embodiment of the present invention is applied. FIG. 4 is a circuit diagram showing an equivalent circuit model of a smoothing capacitor constituting a power supply smoothing LC filter in the DC-DC converter shown in FIG. 3. FIG. 5 is a graph showing a change in capacitance according to a DC voltage applied to a smoothing capacitor whose equivalent circuit model is shown in FIG. 4 as a rate of change. FIG. 4 is a circuit diagram showing an equivalent circuit model of a choke coil constituting a power supply smoothing LC filter in the DC-DC converter shown in FIG. 3. It is a graph which shows the change (DC superposition characteristic) of the inductance in each load current of the choke coil by which an equivalent circuit model is shown in FIG. In this Embodiment, it is explanatory drawing used for description at the time of calculating | requiring the impedance of the choke coil in the load current of the level which exists among several levels calculated | required by interpolation complementation. It is a Bode diagram which represents the transfer function of the power supply smoothing LC filter calculated by the present embodiment in comparison with the transfer function calculated by a one-element model.

  Next, the case where the method for deriving the equivalent circuit model of the power supply smoothing LC filter according to the embodiment of the present invention is applied to the power supply smoothing LC filter in the step-down DC-DC converter will be described.

  The step-down DC-DC converter 1 is shown in a circuit diagram in FIG. 3 and includes a PWM switch block 2, an LC filter block 3, and a constant voltage control unit block 4.

The PWM switch block 2 is provided with the input voltage V _in to the input terminal 1a smoothed by the capacitor C _in . In the PWM switch block 2, the two MOSFETs (Moss structure field effect transistors) Q1 and Q2 are switched by the control circuit 5 so that the input voltage Vin is converted into a pulse train. Further, the duty cycle ratio of the output pulse train is changed by switching the MOSFETs Q1 and Q2, and the average value of the output pulse train is set to a desired output voltage. The LC filter block 3 includes a choke coil L and a smoothing capacitor _Cout . The choke coil L and the smoothing capacitor _Cout constitute a power supply smoothing LC filter, which attenuates the high-frequency component of the pulse train and smoothes the output voltage of the DC-DC converter 1 to a direct current.

In the constant voltage control block 4, the output voltage V appearing at the output terminal 1b is divided by the resistor R1 and the resistor R2, and is compared with the reference voltage _Vref by the error amplifier 6. An error signal between the output voltage V and the reference voltage V _ref is amplified by the error amplifier 6 and output to the PWM comparator 7. The PWM comparator 7 compares the amplified error signal with a triangular wave or a sawtooth wave, and sends a control signal to the control circuit 5 so that the output voltage of the DC-DC converter 1 becomes a desired value. DC-DC converter 1 is limited by the input voltage V _in, and outputs any of the DC current I and DC voltage V to the output terminal 1b in response to the control signal.

FIG. 4 shows an equivalent circuit model of the smoothing capacitor _Cout constituting the power supply smoothing LC filter.

In the present embodiment, the equivalent circuit model of the smoothing capacitor C _out is the main capacitive element C1 and the inductive element L2 and the resistor element R3 in series with the main resonance circuit 11 formed by connecting in series, resistor and capacitor elements C _i capacitive circuit 12 formed by connecting the elements R _i in parallel, the inductive element L _i and the resistance element R _i and a formed by connecting in parallel an inductive circuit 13, and the capacitor C _i and the inductive element L _i resistance A sub-resonant circuit 14 formed by connecting the element R _i in parallel is connected. Here, the subscript i of each element indicates a node number, and in these circuits 12 to 14, i = 4 to 15 is set. Each of the circuits 12 to 14 is represented as a parallel circuit of a capacitive element C _i , an inductive element L _i, and a resistive element R _i , where the inductive element L _i = 0 in the capacitive circuit and the capacitive element C in the inductive circuit. _i = 0. In addition, an insulation resistance IR is connected in parallel to the main capacitive element C1 of the main resonance circuit 11.

In the present embodiment, a laminated ceramic chip capacitor 100 [microfarads] of 3216 size to the smoothing capacitor _{C out.} Table 1 below, in which the values of the elements constituting the equivalent circuit model shown in Figure 4 the smoothing capacitor C _out actually measured, and table data of the measured value.

Here, the blank indicates that the element value = 0 and there is no corresponding element. Also, Table 2 below is a table showing measured values obtained by changing the DC voltage applied to the smoothing capacitor C _out [V] to the measured electrostatic capacitance [F] of a smoothing capacitor C _out.

FIG. 5 is a graph showing the change in capacitance according to the DC voltage applied to the smoothing capacitor C _out as the rate of change from the actual measurement values shown in Table 2 above. The horizontal axis of the graph represents the applied DC voltage [V], and the vertical axis represents the capacitance change rate [%]. As shown in the graph, the capacitance change rate at which the smoothing capacitor _Cout decreases increases gradually as the applied DC voltage increases. When the smoothing capacitor _Cout is a ceramic capacitor as in the present embodiment, the capacitance change rate is expressed as the function k (V) shown in the following equation (1) using the applied DC voltage V as a variable: expressed.

As shown in the equation (1), the capacitance change rate k (V) is expressed as a polynomial of the applied DC voltage V. Here, k _j is a constant, and the capacitance change rate k (V) in the graph shown in FIG. 5 is expressed by the following equation (2).

In the present embodiment, the capacitance of the main capacitive element C1 of the main resonant circuit 11 constituting the equivalent circuit model of the smoothing capacitor _Cout is represented by the equation (2) corresponding to the DC output voltage of the DC-DC converter 1. The equivalent circuit model of the smoothing capacitor _Cout is made to correspond to the DC output voltage V of the DC-DC converter 1 by multiplying the capacitance change rate k (V) to be corrected and correcting the capacitance of the main capacitance element C1. Model.

  FIG. 6 shows an equivalent circuit model of the choke coil L constituting the power supply smoothing LC filter in the DC-DC converter 1 shown in FIG.

Equivalent circuit model of the choke coil L is configured to circuit comprising a resistance element R ₄ in parallel circuit X ₄ of the inductive element L ₃ and the resistance element R ₃ connected in series as a minimum unit. In this embodiment, this minimum unit circuits, circuit X ₃ composed connected capacitive elements C ₁ is in parallel to the series circuit of the circuit X ₁ and the circuit X ₂ are connected in series, it is constituted. Circuit X ₁ is made to a series circuit of a resistance element R ₁ and the capacitor C ₂ is inductive element L ₁ is connected in parallel circuit X ₂ are connected to the resistance element R ₂ and inductive element L ₂ is in parallel Made up.

Such impedance Z _L of the choke coil L represented by the equivalent circuit model, assuming that the respective impedance of the circuit X ₃ and circuit X ₄ each X ₃ and X _4, are represented by the following equation (3).

Wherein each impedance _{X 3} and _{X 4,} when the respective impedance of the circuit _{X 1} and circuit _{X 2} and _{X 1} and _{X 2,} respectively, are expressed by the following equation (4) and (5).

Each impedance _{X 1} and _{X 2} are represented by the following equation (6) and (7).

In the present embodiment, the choke coil L is a 3030 size 4.7 [μH] power inductor. Table 3 below shows the values of the elements constituting the equivalent circuit model of the choke coil L shown in FIG. 6 for a plurality of levels of the DC load current [A] flowing through the choke coil L, and the measured values are shown in Table 3 below. It is a table data.

  FIG. 7 is a graph showing the change (DC superposition characteristics) of the inductance [H] at each load current [A] of the choke coil L. The horizontal axis of the graph represents load current [A], and the vertical axis represents inductance [H]. As shown in the graph, the inductance of the choke coil L gradually decreases as the load current increases.

  The inductances of the choke coil L at the load currents at a plurality of levels shown in Table 3 can be obtained by applying the measured values shown in Table 3 to the equations (3) to (7). . Further, the inductance of the choke coil L at a load current other than the level shown in Table 3 is interpolated from the impedance of the choke coil L for a plurality of levels obtained based on the actually measured values shown in Table 3. Can be obtained.

For example, as shown in FIG. 8, when the desired level of load current i _out is between the level 1 load current i ₁ and the level 2 load current i ₂ , the choke coil L at the desired level of load current i _out is shown. the impedance _{Z L,} the impedance _{Z i2} Prefecture in the load current _{i 2} and the impedance _{Z i1} in the load current _{i 1,} determined by interpolating Kan shown in the following equation (8).

In the present embodiment, as described above, the value of each element constituting the equivalent circuit model of the choke coil L is measured for a plurality of levels of direct current flowing through the choke coil L, and the impedance Z _L of the choke coil _L is determined. The impedance Z _L of the choke coil L for the levels between the plurality of levels is obtained by interpolating from the impedance Z _L of the choke coil L for the obtained levels. Thus, the equivalent circuit model of the choke coil L is a model corresponding to the level of the DC output current I of the DC-DC converter 1.

The power supply smoothing LC filter in the DC-DC converter 1 generally has a transfer function G _LC (ω) expressed by the following equation (9).

Here, ω: angular frequency, C _out : capacitance of smoothing capacitor C _out , L: inductance of choke coil L, ESR _L : real part of impedance of choke coil L, RD _S : on-resistance of MOSFET Q1, R _d : ON resistance of MOSFET Q2, ESR _C : real part of impedance of smoothing capacitor C _out , R _L : output resistance.

Smoothing capacitor _{C out} impedance _Z C corresponding to the applied DC voltage V (V), when the capacitance of the main capacitor element C1 of the main resonance circuit 11 of the equivalent circuit model of the smoothing capacitor _{C out} and C1, the following (10).

Therefore, the values C _out (V) and ESR _C (V) corresponding to the applied DC voltage V of C _out and ESR _{C in} the equation (9) representing the transfer function G _LC (ω) are expressed by the above equation (10). From the represented impedance Z _C (V), it is obtained by the following equations (11) and (12).

Here, Re represents the real part of the impedance _{Z C.} In the present embodiment, when the equivalent circuit model of the power supply smoothing LC filter is derived by obtaining the transfer function G _LC (ω) expressed by the equation (9), as described above, the main capacitance of the main resonance circuit 11 is calculated. The capacitance C1 of the element C1 is multiplied by the capacitance change rate k (V) shown in the equation (2) corresponding to the DC output voltage V of the DC-DC converter 1 as shown in the equation (11). The electrostatic capacitance C1 of the main capacitive element C1 is corrected.

Further, the value according to the level of the load current of ESR _L and L in the equation (9) representing the transfer function G _LC (ω) is the impedance Z _L obtained in the equation (3) or (8 ) from the impedance Z _L as determined by interpolating complete represented in formula, obtained by the following equation (13) and (14).

Here, Re represents the real part of the impedance _{Z L.} In the present embodiment, when the transfer function G _LC (ω) expressed by the equation (9) is obtained to derive the equivalent circuit model of the power supply smoothing LC filter, the impedance Z _L of the choke coil L is derived as described above. Is a value corresponding to the level of the DC load current I of the DC-DC converter 1. As a result, in general, the transfer function G _LC (ω) represented by the equation (9) is a value according to the DC output voltage V and the DC output current I of the DC-DC converter 1 in this embodiment. The function G _LC (ω, V, I) is obtained.

FIG. 9 is a Bode diagram representing the transfer function G _LC (ω, V, I) calculated as described above according to the present embodiment in comparison with the transfer function G _LC (ω) calculated using a one-element model. is there.

As shown in the LC filter block 3 in the circuit diagram of FIG. 3, this one-element model is composed of a one-element choke coil L and a one-element smoothing capacitor _Cout . Further, in this calculation, inductance 4.7 [.mu.H] choke coil L one element model was the electrostatic capacitance value of the smoothing capacitor C _out and the conditions of 47 [μF]. Further, 1.8 a DC output voltage V of the DC-DC converter 1 [V], 1.5 the DC output current I [A], the switching frequency is 400 [kHz], the on-resistance RD _S of MOSFETs Q1 27 [ mΩ], the on-resistance R _{d of the} MOSFET Q2 is 21 [mΩ], and the load resistance _RL is 100 [Ω].

The vertical axis of the Bode diagram is the absolute value [dB] of gain (Gain) and its phase (Phase) [°], and the horizontal axis is frequency ω [Hz]. Further, the gain characteristic A1 according to the present embodiment is represented by a thick solid line, and the phase characteristic A2 is represented by a thick dotted line. The gain characteristic B1 by the one element model is represented by a thin solid line, and the phase characteristic B2 is represented by a thin dotted line. As shown in the figure, the gain characteristic A1 according to the present embodiment has a saturated gain attenuation at a high frequency, whereas the gain characteristic B1 based on the one-element model has a monotonically attenuated gain at a high frequency. doing. Further, the phase characteristic A2 according to the present embodiment shows a tendency to return to 0 [°] at a high frequency, whereas the phase characteristic B2 according to the one-element model is 180 [°] at a high frequency. . From this, it can be seen that in the simulation according to the present embodiment, the dynamic characteristics of the choke coil L and the smoothing capacitor _Cout are taken into account, and a behavior close to that of an actual circuit is obtained.

According to the present embodiment, as described above, the equivalent circuit model of the smoothing capacitor _Cout is the DC output voltage of the DC-DC converter 1 to the electrostatic capacitance C1 of the main capacitive element C1 constituting the model. The capacitance change rate k (V) corresponding to V is multiplied as shown in the equation (11), and the capacitance C1 of the main capacitance element C1 is corrected, whereby the DC output of the DC-DC converter 1 is corrected. A model corresponding to the voltage V is used. Further, the equivalent circuit model of the choke coil L is obtained by obtaining the impedance Z _L of the choke coil L according to the equation (3) for a plurality of levels of the direct current I flowing through the choke coil L, and for the levels between the plurality of levels. The impedance Z _L of the choke coil L is obtained by interpolating and complementing the impedance Z _L of the choke coil L for the plurality of obtained levels using the equation (8), whereby the DC output of the DC-DC converter 1 is obtained. The model corresponds to the level of the current I. Therefore, the equivalent circuit model of the power source smoothing LC filter derived from the equivalent circuit models of the choke coil L and the smoothing capacitor is accurately derived according to the DC output voltage V and the DC output current I of the DC-DC converter 1. The characteristics of the power supply smoothing LC filter during the operation of the DC-DC converter 1 are accurately expressed. For this reason, the simulation in the circuit design of the DC-DC converter 1 is performed with high accuracy, and it is possible to contribute to the reduction in the number of trials and the shortening of the trial period in the circuit design of the DC-DC converter 1.

In the present embodiment, the measured values of the elements constituting the equivalent circuit model of the smoothing capacitor _Cout shown in FIG. 4 are converted into table data as shown in Table 1, and the choke coil L shown in FIG. The measured values of each element for a plurality of levels constituting the equivalent circuit model are converted into table data as shown in Table 3, so that the transfer function G _LC (ω, V, I) is obtained and the power supply smoothing LC filter is obtained. in deriving the equivalent circuit model, easily, and you can calculate the impedance Z _L of the impedance Z _C and the choke coil L of the smoothing capacitor C _out, easily, depending on the DC output voltage V of the DC-DC converter 1 deriving an equivalent circuit model of the choke coil L, which corresponding to the equivalent circuit model and the DC-DC converter 1 of the DC output current I of the smoothing capacitor C _out Rukoto can. Therefore, it becomes possible to use to easily reproduce the equivalent circuit model of the choke coil L and a smoothing capacitor C _out during the operation of the DC-DC converter 1.

In the present embodiment, the equivalent circuit model of the smoothing capacitor _Cout is such that the capacitive circuit 12, the inductive circuit 13, and the sub-resonant circuit 14 are connected in series to the main resonant circuit 11, as shown in FIG. The capacitance change rate k (V) corresponding to the DC output voltage V of the DC-DC converter 1 is multiplied by the main capacitance element C1 constituting the main resonance circuit 11, and the main resonance circuit 11 is The electrostatic capacitance of the main capacitive element C1 is corrected. For this reason, the characteristic of the main resonance circuit 11 that most significantly represents the characteristic of the smoothing capacitor _Cout is corrected, and the electrostatic capacitance of the smoothing capacitor _Cout is most effective in accordance with the DC output voltage V of the DC-DC converter 1. It is corrected to.

Further, in the present embodiment, the equivalent circuit model of the choke coil L, as shown in FIG. 6, a resistance element R ₄ connected in series with the parallel circuit X ₄ of the inductive element L ₃ and the resistance element R ₃ As a minimum unit, the circuit is configured in various ways according to the accuracy and purpose of the simulation of the DC-DC converter 1.

In the above embodiment, the equivalent circuit model of the choke coil L of an equivalent circuit model and the plurality of levels of the smoothing capacitor C _out, and the table data of in response to each type of the smoothing capacitor C _out and the choke coil L Alternatively, it may be configured as a library.

According to this configuration, the table data (see Table 1) regarding the measured values of the elements constituting the equivalent circuit model of the smoothing capacitor C _out and the measured values of the elements configuring the equivalent circuit model of the choke coil L are described. The table data (see Table 3) can be immediately extracted from the library according to each type of the smoothing capacitor _Cout and the choke coil L used in the DC-DC converter 1 to be simulated. For this reason, each equivalent circuit model of the choke coil L and the smoothing capacitor C _out during the operation of the DC-DC converter 1 depends on each type of the smoothing capacitor C _out and the choke coil L used in the DC-DC converter 1 to be simulated. Easily derived immediately.

In the above embodiment, the equivalent circuit model of the smoothing capacitor _Cout is illustrated as shown in FIG. 4, and the equivalent circuit model of the choke coil L is configured as shown in FIG. The shape of the circuit model is not limited to these. For example, the equivalent circuit model of the smoothing capacitor _Cout may be configured by connecting at least one of the capacitive circuit 12, the inductive circuit 13, and the sub-resonant circuit 14 to the main resonant circuit 11 in series. Good.

The method for deriving the equivalent circuit model of the present embodiment described above can be easily used by using the following computer program. The computer program includes a first step for inputting the types of the smoothing capacitor _Cout and the choke coil L, and a second step for inputting the values of the DC output voltage V and the DC output current I of the DC-DC converter 1. The equivalent circuit model (see FIG. 4) of the table data (see Table 1) prepared in advance for the type of smoothing capacitor _Cout input in the first step is selected from the library, and the selected smoothing capacitor C _By calculating the impedance Z _C of the smoothing capacitor C _out by the expression (10) using the equivalent circuit model of _out, the equivalent circuit model of the smoothing capacitor C _out is determined according to the DC output voltage V input in the second step. The third step of making the model and the type of choke coil L input in the first step. A prepared table data equivalent circuit model (see Table 3) (see FIG. 6) selected from the library Te, the impedance Z _C of the choke coil L using the equivalent circuit model of the choke coil L selected A fourth step in which the equivalent circuit model of the choke coil L is a model corresponding to the DC output current I input in the second step by calculating using the equations (3) and (8), Using the equivalent circuit model of the smoothing capacitor C _out derived in the step and the equivalent circuit model of the choke coil L derived in the fourth step, the transfer function G _LC (ω, V, I) of the power source smoothing LC filter is expressed by (9 ) To obtain the equivalent circuit module of the power supply smoothing LC filter corresponding to the DC output voltage V and DC output current I input in the second step. And a fifth step of deriving Le, to function method of deriving the equivalent circuit model of the LC filter power supply smoothing of the present embodiment described above.

The method for deriving the equivalent circuit model of the power supply smoothing LC filter of the present embodiment includes the types of the smoothing capacitor _Cout and the choke coil L constituting the DC-DC converter 1 to be simulated, and the DC output of the DC-DC converter 1. Each value of the voltage V and the DC output current I is input to the computer program, so that the computer program functions as described above. In other words, the equivalent circuit model of the smoothing capacitor C _out is automatically set to a model corresponding to the input type smoothing capacitor C _out and the input DC output voltage V by the computer program, and the choke coil L The equivalent circuit model is a model corresponding to the input type choke coil L and the DC output current I of the input value. For this reason, the user of this derivation method can determine the types of the smoothing capacitor _Cout and the choke coil L constituting the DC-DC converter 1 to be simulated, and the DC output voltage V and the DC output current I of the DC-DC converter 1. By simply inputting each value into the computer program, an accurate simulation of the DC-DC converter 1 can be easily performed with high accuracy. As a result, an accurate circuit simulation of the DC-DC converter 1 can be accurately and easily performed even by a general user who does not have specialized knowledge regarding circuit simulation.

  Further, the computer program can be used from a terminal such as a personal computer connected to the Internet network by accessing a server such as an electronic component manufacturer having the computer program via the Internet network. According to this configuration, the user can easily use the computer program by accessing a server including the computer program from a terminal connected to the Internet network. Therefore, it is possible to provide a large number of users with a method for deriving an equivalent circuit model of the power supply smoothing LC filter according to the present embodiment.

DESCRIPTION OF SYMBOLS 1 ... Step-down DC-DC converter 2 ... PWM switch block 3 ... LC filter block 4 ... Constant voltage control part block 5 ... Control circuit 6 ... Error amplifier 7 ... PWM comparator 11 ... Main resonance circuit 12 ... Capacitive circuit 13 ... Induction Circuit 14 ... sub-resonant circuit _Cout ... smoothing capacitor L ... choke coil C1 ... main capacitance element

Claims (6)

For power source smoothing, an equivalent circuit model of a power source smoothing LC filter composed of a choke coil and a smoothing capacitor for stabilizing the output voltage of a DC stabilized power source circuit is derived from each equivalent circuit model of the choke coil and the smoothing capacitor. In a method for deriving an equivalent circuit model of an LC filter,
The equivalent circuit model of the smoothing capacitor includes a capacitive circuit formed by connecting a capacitive element and a resistive element in parallel, an inductive circuit formed by connecting an inductive element and a resistive element in parallel, and a capacitive element and an inductive element. At least one of the sub-resonant circuits formed by connecting the resistive elements in parallel is configured to be connected in series to the main resonant circuit formed by connecting the main capacitive element, the inductive element, and the resistive element in series,
The capacitance change rate of the smoothing capacitor according to the applied DC voltage applied to the smoothing capacitor is measured and expressed as a function with the applied DC voltage as a variable, and the electrostatic capacitance of the main capacitive element constituting the main resonance circuit is expressed. By correcting the capacitance of the main capacitive element by multiplying the capacitance by the capacitance change rate according to the DC output voltage of the DC stabilized power supply circuit, the equivalent circuit model of the smoothing capacitor is converted to the DC stable Model according to the DC output voltage of the power supply circuit,
The value of each element constituting the equivalent circuit model of the choke coil is measured for a plurality of levels of direct current flowing through the choke coil, and the impedance of the choke coil is obtained for the plurality of levels, The impedance of the choke coil with respect to the level between them is obtained by interpolating from the impedances of the choke coil with respect to the plurality of levels that have been obtained, so that the equivalent circuit model of the choke coil is determined as the DC stabilized power supply. A method for deriving an equivalent circuit model of a power source smoothing LC filter, characterized in that the model is based on the level of the DC output current of the circuit. The measured value of each element constituting the equivalent circuit model of the smoothing capacitor is converted into table data, and the equivalent circuit model of the smoothing capacitor that is converted into table data when the equivalent circuit model of the power source smoothing LC filter is derived Using the equivalent circuit model of the smoothing capacitor as a model according to the DC output voltage of the DC stabilized power supply circuit,
The choke coil that has been converted into table data for the plurality of levels of measured values of each element constituting the equivalent circuit model of the choke coil, and converted into table data when the equivalent circuit model of the power source smoothing LC filter is derived. The equivalent circuit model of the choke coil is a model corresponding to the DC output current of the DC stabilized power supply circuit using each equivalent circuit model of the equivalent circuit model of claim 1, How to derive a circuit model.   An equivalent circuit model of the smoothing capacitor and an equivalent circuit model of the choke coil for the plurality of levels are converted into table data according to each type of the smoothing capacitor and the choke coil, and are made into a library. Item 3. A method for deriving an equivalent circuit model of the power supply smoothing LC filter according to Item 2. Equivalent circuit model of the choke coil, either a circuit formed by connecting a resistive element in series with the parallel circuit of the inductive element and the resistive element of claims 1, characterized in that it is configured as a smallest unit of claim 3 A method for deriving an equivalent circuit model of the power supply smoothing LC filter according to claim 1. A first step of inputting types of the smoothing capacitor and the choke coil, a second step of inputting respective values of a DC output voltage and a DC output current of the DC stabilized power supply circuit, and the first step. An equivalent circuit model of table data prepared in advance for the input type of smoothing capacitor is selected from a library, and the equivalent circuit model of the smoothing capacitor is selected using the selected equivalent circuit model of the smoothing capacitor. A third step of making a model corresponding to the DC output voltage input in step 2 and an equivalent circuit model of table data prepared in advance for the type of choke coil input in the first step are stored in a library The choke coil is selected using an equivalent circuit model of the selected choke coil. And a fourth equivalent circuit model of the smoothing capacitor derived in the third step, and a fourth equivalent circuit model of the smoothing capacitor derived in the third step. A fifth step of deriving an equivalent circuit model of the power supply smoothing LC filter according to the DC output voltage and DC output current input in the second step using the equivalent circuit model of the choke coil derived in the step; the cause the computer to execute a computer program for executing the method of deriving the equivalent circuit model of the LC filter power supply smoothing of claim 3. 4. The power smoothing LC according to claim 3, wherein a server including the computer program is accessed via an Internet network, and each of the steps is performed by the terminal using the computer program from a terminal connected to the Internet network. 6. The method of using a computer program according to claim 5 , wherein a method for deriving an equivalent circuit model of a filter is implemented .

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